<p>Since the emergence of plaintext-related chaotic image cryptosystems, no targeted cryptanalysis methods have been developed specifically for them. Most of the few published analysis papers adopt approaches designed for plaintext-independent cryptosystems, and these approaches are only effective against specific vulnerabilities. This paper, based on a recently-published plaintext-related encryption algorithm, proposes three novel analysis methods to assess its security. The first method leverages existing research results. By applying the differential method, it decrypts the sub-links of the encryption process one by one. The second method constructs a series of S-boxes through the combination of certain sub-links, which further clarifies the qualitative relationship between plaintext and ciphertext pixels. Once these S-boxes are attacked, the original algorithm can be decrypted. The third method analyzes security from the decryption-end perspective. Owing to specific vulnerabilities, the decryption process of the original algorithm can be reduced to a set of codebooks. Subsequently, the original algorithm can be decrypted by calculating these codebooks. Notably, the third approach is an innovation, as it is proposed for the first time in this study. These three analysis methods possess general applicability for the cryptanalysis of common plaintext-related encryption algorithms. Both theoretical derivations and experimental results have verified their feasibility and effectiveness.</p>